High-temperature grease



A. J. MQRWAY HIGH-TEMPERATURE GREASE April 26, 1949.

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'Plnsuln (L M/m2) arnold' d. Dbrw'af Inventor Clbborna A. J. MORWAY HIGH-TEMPERATURE GREASE April 26, 1949.

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Patented Apr. 1949 Y UNITED STATES PATENT oFEicE mon-TEMPERATURE GREASE Arnold J. Morway, Clark, N. J., assigner to Standard Oil Development Company, a corporation of Delaware Application october 1, 1947, serial No. '171,329

'11 claims. '(01.252--42i The present invention relates to a high temgreases of stable structure are usually required, .l perature grease and method of preparing the that is greases which do not melt or separate oil same. More particularly, it relates to a grease from the thickener at temperatures over 350 to of improved structure and stability. It relates 400 F., for example. At the, same time the further to a grease containing a normally water 5 greases must be capable of giving adequate lubrisoluble soap which is treated in a manner. that cation at much lower temperatures. Obviously improves its resistance to oil separation and to they must not be too hard or stii to give proper oxidation and tends to insolubilize said soap in protection at ordinary temperatures even though water and thereby tends to reduce leaching of their principal use is for high temperature opthe soap from the grease with consequent deloeration. y v f terioration of the lubricant. It has been customary in the past to raise the In the prior art, numerous lubricating grease melting point of certain greases, for example compositions have been proposedv having various sodium soap greases, by increasingthe percentage characteristics such as high Itemperature conof soap employed in the lubricant. This may be sistency, resistance to leaking or oil separation, 16 satisfactory for some purposes but frequently is r resistance to oxidation,y waterproof properties, objectionable for the reason just suggested that and the like. As a general rule, such composisuch greases are too stiil' for satisfactory lubritions have been prepared by incorporating into cation at normal starting temperatures, requira suitable lubricating oil, usually of mineral oil ing excessive torque and resulting in unsatisfacbase, a metallic soap of fatty oils or fatty acids 2o tory performance where operation may proceed which has the property of thickening the lubrifor' appreciable periods of time at low or even applications of lubricating compositions, the con- Many of the purposes for which high temperaditions of use are such that liquid compositions ture lubricants are required involve other adverse are unsatisfactory because they run out of bear- 25 operating conditions. For example, lin many ings or other parts tobe lubricated unless a suitcases there is a marked tendency to oxidation able oil sump is provided, or they are readily and some tendency to deteriorate because of washed away or otherwise rendered ineffective. moisture in a humid atmosphere or water may MOreOver, they do not furnish a good seal against be present in liquid form which tends to leach dirt and dust. For such purposes. lubricating ao out the soap from the voil anowing the lubricant ereases have an importent field 0f use, it being to 1eak away from the bearing and have the bearparticularly important' that during all types of ing unprotected use they retain a given required consistency so It is, therefore, an object of the present inas to remain in place and perform their lubriventina to improve the high temperature stacting and sealing mmm A Particular a9' -as bility, oxidationstabinty, and to some extent to p :cation of lubricating greases' for example 1S improve the moisture-resisting properties of 1urlllsetinlse,kartg'iggnmerigi i? Ifz'g `liricating greases, particularly lubricating 'greases high temperatures and due either to the high of the `sodium soap or other alkali metal soap temperatures or to the churning action of the o tYPe- It is a further object 0f thi invention t0 bearings, many types of eases become too soft secure such improvements by the use of simple or fluid at elevated temperatures to remain in and inexpensive materials and process steps.v situ and properly perform their lubricating func- Other and further objects will appear as this detions. For such purposes, high temperature scription proceeds.

Normal ball bearing greases and other socalled high temperature lubricants, which are usually prepared from sodium soaps and irom mineral lubricating oils having a viscosity which may vary from about .00 or 100 to 1000 S. S. U'. at 100 F., usually melt at a temperature in the neighborhood of 350 F. to 400 F. Even higher melting points may be obtained by using cylinder oils and bright stocks of high viscosity or, as indicated above, by increasing the soap content. Both of these methods, however, produce greases which require excessive starting torques at low or even at normal temperatures and result in unsatisfactory lubrication at the lower temperatures of operation. It has been found that the addition of small quantities of unsaturated low molecular weight mono-basic acids to the fatty acids or fats employed in the soaps used in lubricating grease manufacture results in very marked improvement as regards the melting point, physical structure stability, oxidation resistance, and other important properties. A particularly suitable low molecular weight acid is acrylic acid,

as will be evident from the following examples.

Four greases were prepared using the same procedure. Three of the greases contained acrylic acid, and the fourth, for comparison, contained no low molecular weight unsaturated acid. In each casel fatty acids and about one-third of the mineral oil were first charged to a nre-heated kettle and the temperature was raised to 150 F. and held there until all the solid fatty materials had melted. When the unsaturated acid, specifically acrylic acid, was used, it was added and immediately thereafter the alkali, sodium hydroxide, was added as a 30% aqueous solution.

The temperature was next raisedto about 220 F. while agitating until the soaps were substantially dehydrated. The remainder of the mineral oil was then added to the kettle in small quantities progressively while the temperature was raised to about 300 F. Thereafter the temperature of the grease was raised further to about 500 F. and the heating was then discontinued. During these heating operations, stirring was continuous.

While the composition was permitted to cool down to about 200 F., stirring was continued. At this temperature the grease` was` withdrawn from the kettle, filtered and packaged.

The formulas which were employed are shown below.

EXAMPLE I 4 Per cent Oleic acid Hydrogenated fish oil acids 10 Sodium hydroxide 5.4

Acrylic acid cH2=cHcooH 2.o Mineral lubricating oil (500 S. S. U. viscosity Per cent Acrylic acid 2.0 Phenyl alpha naphthylamine--- 1.0

Mineral lubricating oil (500 S. S. U. viscosity at F. from low cold test crude) 78.0

Forl purposes ol' comparison with the greases,

of Examples I, II, and III, another grease was prepared, omitting the unsaturated low molecular weight acid but` increasing the soap content in order to obtain a grease of comparable consistency.

EXAMPLE IV Per cent 60% hydrogenated fish oil acid, 40% oleic acid 25.00 Glycerine 2 .50 50/50 sodium sulfonates and oil 1.00 Phenyl alpha naphthylamine 1.00 Sodium hydroxide 4.50

Mineral lubricating oil (5.00 S. S. U. viscosity at 100 F. from low cold test crude) 66.00

Comparative physical properties of these four examples are given in Table I.

TABLE I Properties of acrylic acid greases The superior propertiesof the greases of Examples I, II, and III which contained acrylic acidl will be evident from the data in Table I. In particular, it will be noted that the addition of acrylic acid to the greases raises their dropping points considerably. The acrylic acid greases had lower penetrations both before and after working. showing their improved consistency and resistance to shear breakdown. The grease of Example I showed satisfactory low oil separation characteristics, only 3.2% separation occurring after 50 hours at 250 F. Figure I is a graph showing the eect of changes in temperature on the pressure viscosity of greases prepared with and without acrylic acid. As shown in this figure, the acrylic acid-containing greasespossess excellent high temperature consistency properties, not becoming viscous and rubbery as does the usual commercial high temperature grease above about 300 F. Moreover, they do not become excessively iiuid at high temperatures as is 'the case with other types of greases.

The superior properties of greases prepared according to the invention described herein containing small amounts of low molecular weight unsaturated aliphatic acids are also shown by Examples V, VI, VII, and VIII listed in Table II. The data given in this table show that these greases are more resistant to oxidation and oil separation `if the finished greases are slightly alkaline rather than acidic in reaction.

Tsaar.' II

Properties of acrylic acid creases Example Desi ti Grrmglm gna VIH yra e om- V VI VII (no acrylic Gmercial rease (no acid present) acrylic acid present) Formulation:

Acrylic acid per cent-- 2. 0 2 0 2. 0 Hydrogenated iish oil acids .-do.-.- 8. 8. 0 8.0 Oleicncid do l 2.0 2.0 2.0 Sodium hydroxide.- -.do.... 2. 8 2 5 2. 3 Phenyl alphana hth lamine --do..-. 0.5 0.5 0.5 Mineral lubrica g o (500 S. S. U. Viscosity at 100 F.

from low cold test crude) per cent.. 84. 7 85 0 85. 2 ty or acidity -.d0-..- 10. 30 l 0. 08 I 0. 45 Penetration, mm./l0:

A npeamnm n Smooth Smooth Unworked mi) 170 226 60 Stroh 205 194 260 100,000 Strokes (Five hole worker plate) 192 32) 250 Oil Separation:

Storage none trace trace trace-none 50 Hours at 210 F per cent.. 4. 2 4. 5 15. 6 2. 5 Ford Wheel Test, e Hours at 211 F do none none 25 none ASTM dropping goint. "F 450 388 400 364 450-500 Norma-Rodman omb Oxidation Test (Hours to p. s. i. v

drop) 190 296 36 110-170 High Temperature/Pressure Vis. Pressure at 350 F. N W W hm T t t l tpounds-- 7.5 6.0 2.5 26

avy ar as g es,percengreaseossa- 75 F 5 7 0 100 100 F 10 m 6 1 As NaOH. 2 As oleic acid.

The data, in Table II also demonstrate the improvement in water resistance obtained by the addition of acrylic acid to the grease formulation.

Figure 2 is a graph showing the eiect of changes in temperature on the pressure viscosity of alkaline and acid acrylic acid greases in comparison with a premium-grade commercial grease. As can be seen from this figure, neither type of acrylic acid grease exhibits the abrupt change to a viscous, rubbery material shown by the commercial high temperature grease. The alkaline grease, however, is even more desirable than the acidic one, showing less tendency to become excessively fluid with an increase in temperature.

In the examples given above. hydrogenated sh oil acids and oleic acidswere used to prepare the soaps and the saponifying material usedy was Y sodium hydroxide. However, stearic acid, beef fat, tallow, or linoleic or linolenic acids may be used or the saturated or unsaturated glycerides or various fatty acids may be `employed with or without the addition of polyethylene glycol. Polyethylene glycol plasticlzes these greases to a.` marked degree but by doing this it lowers the dropping point (melting point) considerably. In lieu of sodium hydroxide the hydroxides or oxides of other alkali or alkaline earth metals may be used. Thus calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, or corresponding oxides or suitable carbonates may be employed. These materials may be mixed in various proportions as will be apparent to those skilled in the art.

In lieu of acrylic acid, I may employ other monobasic unsaturated acids of low molecular weight, particularly unsaturated monobasic aliphatic acids having 3 or 4 carbon atoms per mole,- cule, such as methacrylic acid cr crotonic acid. Other related compositions may be used with some success although the foregoing arev those preferred. Thus where properties desired are not too critical some of the saturated acids ci closely rented composition, ma as :imac ma apn "5 of the acids. Preferably. also, the soap is an alkali or beta hydroxy butyric acid, and acetcacetlc acid may also be used, though less 'desirable than the unsaturated materials mentioned above.

The quantities o`f these acids and related materials which may be used may be varied widely depending upon the particular characteristics desired. Preferably the quantity used vwill be not less than about 0.1% and not more than about 5% by weight, based upon the nished lubricant. These proportions are based on the acid or acidogenic material prior to the neutralization or subi stantial neutralization which occurs when the saponifying agent is added.` The weight propor-4 tions of salt, resulting from such neutralization, will be comparable though somewhat higher because of the inclusion of the metal ion. The grease composition otherwise will normally consist essentially of 60 to 95% by weight of a mineral base oil having a viscosity of about to 1000 S. S. U. or more at F. For most purposes the viscosity preferably does. not exceed 600 or 700 S. S. U. at 100 F. The soap which is preferably a sodiumy soap of fatty material but which alkaline earth metal soap, or mixtures thereof, will normally be used in proportions of 5 to 35%, based on the weight of the finished lubricant. A soap content between about 8 and 20% is ordinarily preferred. f

From the foregoing, it will be understood that the invention in its broader aspects includes a lubricating grease compositionof mineral oil base thickened to a grease-like consistency by incorporating in the il a suitable metal soap of fatty oil or fatty acid. The acid used, preferably acrylic acid, is preferably addedto the grease before saponincation of thefatty material. As pointed out below, acid forming nitriles may be used instead I-metal soap, especially sodium soap, or lithium soap. having superior high temperature. properties.k The sodium soap is especially preferred where water solubility is not a serious matter.

may be lithium or other alkali metal soaps or an 7 Greases oi this character have high melting points or dropping points without the usual high soap content which makes them undesirable for y lubricating at low or normal temperatures.

From the data in Table II it will be understood that a satisfactory and representative composition may include about 10% of fatty acids, 2 to 2.8% of alkali (preferably sodium hydroxide), 2.0% of acrylic acid (methacrylic acid or crotonic acid may also be used though somewhat inferior) and a small amount, less than 1% of a conventional antioxidant such as phenyl alpha naphthylamine. Obviously the alkali (e. g. sodium hydroxide) serves both to saponify the higher fatty acid and to form a salt with the acrylic or other low molecular acid.

It will be understood that other conventional additives may be used in greases made according to the present invention, such as tackiness agents, viscosity index improvers, anti-corrosion agents, extreme pressure additives, and the like, as will be apparent to those skilled in the art.4

In lieu of acrylic acid, acrylonitrile may be added prior to saponication, and this material appears to hydrolyze during the grease cooking to form the acid. It will be understood that reference in the claims to acidogenic materials includes usual type of inhibitors `for the unsaturated nitrile, such as phenyl alpha naphthylamine must be added 'to the reaction mixture. The formulation and method of manufacture are given below.

Formulation Percent Hydrogenated ilsh oil acids 8.0 Oleic `acid 2.0 Acrylonitriie 2.5 NaOH 3.2 Phenyl alpha naphthylamine 0.5

Mineral lubricating oil (500 S. S. U. viscosity 100 F. from low cold test crude) 83.0

The acids and one-third of the oil were added to a kettle and heated to 150 F. The acrylonitrile was then added and immediately thereafter the aqueous solution (40%) of sodium hydroxide. Ammonia was evolved immediately. The mixture was stirred while holding temperature below 150 F. When all ammonia ceased coming oil. the temperature was raised to 250 F., the balance of the oilwas added, and the grease was further heated to 500 F. The molten grease was cooled to 90-110" Il'. by passing through a grease cooler.

Properties of grease Pei-oen: free alkalinity 0.25 a's Noon Unworked penetration mm./10 254 Worked penetration mm./10 245 100.000 stroke penetration (live hole worker) 315 8 Formulation Per cent Hydrogenated iish oil acids 10.0 Acrylonitrile 3.0 LiOH-HzO 3.1 Phenyl alpha naphthylamine 0.5

Mineral lubricating oil (58 S. S. U. viscosity at F. from low cold test crude) 83.4

'I'he same method of manufacture was employed as that given above. The grease was ol excellent smooth appearance and was extremely stable to shearing stresses.

Worked penetration mm./10 275 100,000 stroke penetration mm./ 10 (iive hole worker plate) f 3.--- 285 Dropping point F. 465

Per cent free alkalinity as NaOH 0.43

I claim:

1. A lubricating grease composition consisting essentially of a mineral base lubricating oil thickened to a grease consistency with a fatty material which has been saponiiied withy a compound selected from the alkali metal and alkaline earth metal hydroxides, oxides and mixtures thereof, said composition containing the metal salt resulting from the reaction of said metal hydroxide with 0.1 to 5% by weight of an unsaturated aliphatic monobasic acidogenic material having 3 to 4 carbon atoms.

. 2. A lubricating grease composition consisting essentially of a mineral base lubricating oil thickened to a grease consistency with an alkali metal soap of fatty material, said composition containing the alkali metal salt obtained from 0.1 to 5% by` weight of an unsaturated aliphatic monobasic .acidogenic material having 3 to 4 carbon atoms per molecule.

3. A lubricating grease compositionfconsisting essentially of 60 to 95% by weight of mineral base lubricating oil, 5 to 35% of alkali metal soap, and alkali metal salt of 0.1 to 5% of an unsaturated aliphatic monobasic acid having 3 to 4 carbon atoms per molecule.

4. A lubricating grease composition consisting essentially of 60 to 95% by weight of a minerai base lubricating oil, 5 to 35% of an alkali metal soap of fatty material and the alkali metal o! 0.1 to 5% of acrylic acidogenic material.

5. A lubricating grease composition consisting essentially of 60 to 9.5% by weight of a mineral base lubricating oil, 5 to 35% sodium soap of fatty material, and the sodium salt of 0.1 to 5% of acrylic acid for the purpose of decreasing the solubility of said' sodium soap in water.

6. A lubricating grease composition consisting essentially of 60 to 95% by weight of mineral lubricating oil, v5 to 35% of the sodium soaps of oleic acid and hydrogenated fish oilacids, and the sodium salt oi 0.1 to 5.0% of an unsaturated aliphatic monobasic acid having 3 to 4 carbon atoms per molecule.

7. A lubricating grease composition consisting essentially o1' 'I7 to 91% by weight of mineral base lubricating oil, 8 to 20% of sodium'soap of fatty material, and the sodium salt oi 1 to 3% of acrylic acid.

8. A composition as in `claim 'l having a slightv excess of alkali.

9. A composition as in claim 1 having a. slight excess oi alkali.

excess or alkali,

9 li. A lubricating grease composition consisting essentially of about 85% by weight of mineral oil,

together with the reaction products of 10% fatty acids, 2.o to 2.8% sodium hydroxide, 2.0% acryuc acid. and including a fraction of 1% o1' an antl- 5 oxidant.

ARNOLD J. MORWAY. I

EEFERENCES CITED The following references are of record in the 10 me of this patent:

. l0 UNITED STATES PATENTS Number 

